Display device, driving method, and electronic apparatus

ABSTRACT

A display device according to the disclosure includes: a display section having a plurality of unit pixels; and a driving section that, in a first drive mode, performs write driving and thereafter performs light emission driving in a plurality of light-emitting periods on each of the unit pixels. One of predetermined number of light-emitting periods out of the plurality of light-emitting periods other than a first light-emitting period is longer than the first light-emitting period, and another one of the predetermined number of light-emitting periods is shorter than the first light-emitting period.

RELATED APPLICATIONS

This application is the U.S. National Phase under 35 U.S.C. § 371 ofInternational Patent Application No. PCT/JP2015/053586, filed on Feb.10, 2015, which in turn claims the benefit of Japanese Application No.2014-092770, filed on Apr. 28, 2014, the disclosures of whichApplications are incorporated by reference herein.

TECHNICAL FIELD

The disclosure relates to a display device that displays an image, amethod of driving such a display device, and an electronic apparatusincluding such a display device.

BACKGROUND ART

Recently, enhanced and increased functionality of electronic apparatuseshas led to development of many electronic apparatuses each including adisplay device built therein, such as tablet terminals and smartphones.The electronic apparatus with the built-in display device as describedabove makes it possible to provide a user with various pieces ofinformation, thus achieving a superior user interface.

By the way, each pixel in a display device typically retains a writtenpixel voltage while emitting light at luminance according to this pixelvoltage. In this case, each pixel may fail to sufficiently retain thepixel voltage, and the pixel voltage may therefore vary with time. Tosuppress degradation of image quality derived from such variation inpixel voltage, various techniques have been developed. As an example,Patent Literature 1 discloses a display device that gradually increasesa peak luminance level over a continuous length of time.

CITATION LIST Patent Literature

Patent Literature 1: Japanese Unexamined Patent Application PublicationNo. 2008-33066

SUMMARY OF INVENTION

As described above, there has been a demand for improved image quality,and further improvements in the image quality have been expected in adisplay device.

It is therefore desirable to provide a display device, a driving method,and an electronic apparatus that make it possible to enhance imagequality.

A display device according to one embodiment of the disclosure includesa display section and a driving section. The display section has aplurality of unit pixels. The driving section, in a first drive mode,performs write driving and thereafter performs light emission driving ina plurality of light-emitting periods on each of the unit pixels. One ofpredetermined number of light-emitting periods out of the plurality oflight-emitting periods other than a first light-emitting period islonger than the first light-emitting period, and another one of thepredetermined number of light-emitting periods is shorter than the firstlight-emitting period.

A display device according to another embodiment of the disclosureincludes a display section and a driving section. The display sectionhas a plurality of unit pixels. The driving section, in a first drivemode, performs write driving and thereafter performs light emissiondriving in a plurality of light-emitting periods on each of the unitpixels. Of time intervals between start timings of adjacent ones of thelight-emitting periods, one time interval is different from another timeinterval.

A driving method according to one embodiment of the disclosure includes:preparing an image signal; in a first drive mode, performing writedriving based on the image signal and thereafter performing lightemission driving in a plurality of light-emitting periods on each ofunit pixels. Upon the light emission driving, one of predeterminednumber of light-emitting periods out of the plurality of light-emittingperiods other than a first light-emitting period is set to be longerthan the first light-emitting period, and another one of thepredetermined number of light-emitting periods is set to be shorter thanthe first light-emitting period.

An electronic apparatus according to one embodiment of the disclosureincludes the foregoing display device. Examples of the electronicapparatus may include a television apparatus, an electronic book, asmartphone, a digital camera, a laptop personal computer, a videocamera, and a head mount display.

In the display device, the driving method, and the electronic apparatusaccording to the respective embodiments of the disclosure, the writedriving is performed and the light emission driving is performedthereafter in the plurality of light-emitting periods. One of thepredetermined number of light-emitting periods out of the plurality oflight-emitting periods other than the first light-emitting period is setto be longer than the first light-emitting period, and another one ofthe predetermined number of light-emitting periods is set to be shorterthan the first light-emitting period.

In the display device according to another embodiment of the disclosure,the write driving is performed and the light emission driving isperformed thereafter in the plurality of light-emitting periods. In thiscase, of the time intervals between the start timings of adjacent onesof the light-emitting periods, one time interval is different fromanother time interval.

According to the display device, the driving method, and the electronicapparatus of the respective embodiments of the disclosure, one of thelight-emitting periods is set to be longer than the first light-emittingperiod, and another one of the light-emitting periods is set to beshorter than the first light-emitting period. This makes it possible toenhance image quality.

According to the display device of the another embodiment of thedisclosure, of the time intervals between the start timings of adjacentones of the light-emitting periods, one time interval is set to bedifferent from another time interval. This makes it possible to enhanceimage quality.

It is to be noted that the effects described above are not necessarilylimiting, and any other effects described in the disclosure may beprovided.

BRIEF DESCRIPTION OF DRAWINGS

FIG. 1 is a block diagram illustrating an exemplary configuration of adisplay device according to some embodiments of the disclosure.

FIG. 2 is a block diagram illustrating an exemplary configuration of adriving section and a display section illustrated in FIG. 1.

FIG. 3 is a circuit diagram illustrating an exemplary configuration of asub-pixel illustrated in FIG. 2.

FIG. 4 is a schematic diagram illustrating exemplary operation of thesub-pixel illustrated in FIG. 2.

FIG. 5 is an explanatory diagram illustrating exemplary operation of acontroller illustrated in FIG. 1.

FIG. 6 is an explanatory diagram illustrating another exemplaryoperation of the controller illustrated in FIG. 1.

FIG. 7 is a timing waveform chart illustrating exemplary operation ofthe sub-pixel illustrated in FIG. 2.

FIG. 8 is a timing waveform chart illustrating another exemplaryoperation of the sub-pixel illustrated in FIG. 2.

FIG. 9 is an explanatory diagram illustrating exemplary operation of acontroller according to a first embodiment.

FIG. 10 is an explanatory diagram illustrating exemplary operation of acontroller according to Comparative Example.

FIG. 11 is an explanatory diagram illustrating exemplary operation of acontroller according to a modification of the first embodiment.

FIG. 12 is another explanatory diagram illustrating another exemplaryoperation of the controller according to the modification of the firstembodiment.

FIG. 13 is a block diagram illustrating an exemplary configuration of adisplay device according to another modification of the firstembodiment.

FIG. 14A is an explanatory diagram illustrating exemplary operation ofthe display device illustrated in FIG. 13.

FIG. 14B is an explanatory diagram illustrating another exemplaryoperation of the display device illustrated in FIG. 13.

FIG. 15 is a block diagram illustrating an exemplary configuration of adisplay device according to another modification of the firstembodiment.

FIG. 16 is an explanatory diagram illustrating exemplary operation of acontroller according to a second embodiment.

FIG. 17 is an explanatory diagram illustrating exemplary operation of acontroller according to a modification of the second embodiment.

FIG. 18 is an explanatory diagram illustrating exemplary operation of acontroller according to another modification of the second embodiment.

FIG. 19 is an explanatory diagram illustrating exemplary operation of acontroller according to another modification of the second embodiment.

FIG. 20 is an explanatory diagram illustrating exemplary operation of acontroller according to another modification of the second embodiment.

FIG. 21 is a perspective view of an external configuration of asmartphone to which a display device according to one embodiment isapplied.

FIG. 22 is a circuit diagram illustrating an exemplary configuration ofa sub-pixel according to another modification.

DESCRIPTION OF EMBODIMENTS

Some embodiments of the disclosure will be described below in detailwith reference to the drawings. It is to be noted that the descriptionwill be given in the following order.

1. First Embodiment

2. Second Embodiment

3. Exemplary applications

1. First Embodiment Exemplary Configuration

FIG. 1 illustrates an exemplary configuration of a display deviceaccording to the first embodiment. A display device 1 may be an activematrix type of display device including organic EL (electroluminescence) elements. It is to be noted that a driving methodaccording to some embodiments of the present disclosure will be embodiedby this embodiment and therefore described together therewith.

The display device 1 may display an image on the basis of an imagesignal Spic. In this example, the image signal Spic includes luminanceinformation IR on a red color (R), luminance information IG on a greencolor (G), and luminance information IB on a blue color (B). The displaydevice 1 may include a driving section 30, a display section 40, aquiescent level detector 20, a controller 11, and a signal processor 12.

The driving section 30 drives the display section 40 on the basis of animage signal Spic2 and a control signal CTL. The display section 40displays an image on the basis of driving operation performed by thedriving section 30.

FIG. 2 illustrates an exemplary configuration of the driving section 30and the display section 40. The display section 40 may include aplurality of pixels Pix that are arranged in a matrix fashion. Each ofthe pixels Pix may include a sub-pixel 9R for a red color (R), asub-pixel 9G for a green color (G), and a sub-pixel 9B for a blue color(B). It is to be noted that, hereinafter, the term “sub-pixel 9” will beused where appropriate to refer to any one of the sub-pixels 9R, 9G, and9B. The display section 40 includes: a plurality of scan lines WSL and aplurality of power lines PL that extend in a row direction (a lateraldirection); and a plurality of data lines DTL that extend in a columndirection (a longitudinal direction). The scan lines WSL, the powerlines PL, and the data lines DTL each have one end that is coupled tothe driving section 30.

FIG. 3 illustrates an exemplary circuit configuration of the sub-pixel9. The sub-pixel 9 may include a write transistor WSTr, a drivetransistor DRTr, a light emitting element 49, and a capacitor Cs. Inother words, the sub-pixel 9 is configured using two transistors (thewrite transistor WSTr and the drive transistor DRTr) and a singlecapacitor Cs in this example, namely, has a so-called “2Tr1C”configuration.

Each of the write transistor WSTr and the drive transistor DRTr may beconfigured of an n-channel MOS (metal oxide semiconductor) TFT (thinfilm transistor), for example. The write transistor WSTr has a gatecoupled to the scan line WSL, a source coupled to the data line DTL, anda drain coupled to both a gate of the drive transistor DRTr and one endof the capacitor Cs. The drive transistor DRTr has a gate coupled toboth the drain of the write transistor WSTr and the one end of thecapacitor Cs, a drain coupled to the power line PL, and a source coupledto both the other end of the capacitor Cs and an anode of the lightemitting element 49.

The one end of the capacitor Cs is coupled to the gate of the drivetransistor DRTr, etc., whereas the other end of the capacitor Cs iscoupled to the source of the drive transistor DRTr, etc. The lightemitting element 49 may be a light emitting element configured using anorganic EL element. The anode of the light emitting element 49 iscoupled to both the source of the drive transistor DRTr and the otherend of the capacitor Cs, whereas the cathode of light emitting element49 is supplied with a cathode voltage Vcath from the driving section 30.It is to be noted that, although the light emitting element 49 isconfigured using an organic EL element in this example, the lightemitting element 49 is not limited thereto, and may be configured usingany other current-driven light emitting element.

With this configuration, the sub-pixel 9 performs write operation inresponse to the turn-on of the write transistor WSTr, so that apotential difference according to a pixel voltage Vsig (described later)is set between the two ends of the capacitor Cs. Further, the drivetransistor DRTr causes a drive current according to the potentialdifference between the two ends of the capacitor Cs to flow through thelight emitting element 49. As a result, the light emitting element 49emits light at luminance L according to the pixel voltage Vsig.

The driving section 30 may include a scan line driving section 31, apower line driving section 32, and a data line driving section 33. Thedriving section 30 may be formed integrally with the display section 40or may be provided separately from the display section 40, for example,as an integrated circuit (chip).

The scan line driving section 31 sequentially applies scanning signalsWS to the scan lines WSL in accordance with the control signal CTLsupplied from the controller 11, thereby sequentially selecting thesub-pixels 9.

The power line driving section 32 sequentially applies power signals DSto the power lines PL in accordance with the control signal CTL suppliedfrom the controller 11, thereby controlling light-emitting operation andnon-light-emitting operation of the sub-pixel 9. In this example, apower signal DS makes transitions between three voltages Vccp, Vext, andVini. The voltage Vccp is a voltage that supplies a current to the drivetransistor DRTr to thereby cause the light emitting element 49 to emitlight, as will be described later. The voltage Vccp is higher than boththe voltages Vext and Vini. The voltage Vext is a voltage that stopslight emission of the light emitting element 49 and is higher than thevoltage Vinit. The voltage Vini is a voltage that initializes thesub-pixel 9.

The data line driving section 33 generates a signal Sig in accordancewith the image signal Spic2 supplied from the signal processor 12 andthe control signal CTL supplied from the controller 11, and applies thegenerated signal Sig to each of the data lines DTL. The data linedriving section 33 may include a DAC (digital analog converter) 34. TheDAC 34 generates the pixel voltage Vsig (an analog voltage) that givesan instruction on luminance of each sub-pixel 9, on the basis of theluminance information IR, IG, and IB (digital codes) included in theimage signal Spic2. Further, the data line driving section 33alternately provides the pixel voltage Vsig and a voltage Vofs used tomake Vth correction described later, thereby generating the signal Sig.

With this configuration, the driving section 30 initializes thesub-pixels 9, makes corrections (the Vth correction and a μ (mobility)correction) to suppress influence that element variations between thedrive transistors DRTr exert over image quality, and writes the pixelvoltages Vsig, as will be described later.

The quiescent level detector 20 illustrated in FIG. 1 generates aquiescent level LS on the basis of the image signal Spic. The quiescentlevel detector 20 may include a noise filter 21 and a quiescent levelcalculator 22.

The noise filter 21 removes noise from the luminance information IR, IG,and IB included in the image signal Spic. The quiescent level calculator22 determines a moving amount of the image on the basis of the luminanceinformation IR, IG, and IB from which noise has been removed by thenoise filter 21. Further, the quiescent level calculator 22 calculatesthe quiescent level LS on the basis of the determined moving amount.When an image expressed by the image signal Spic is a still image, thequiescent level LS has a high value. When an image expressed by theimage signal Spic is a moving image, the quiescent level LS has a lowvalue. In this example, the quiescent level calculator 22 may include amemory 23. The memory 23 is a frame memory in this example and storesthe luminance information IR, IG, and IB regarding one frame image fromwhich noise has been removed by the noise filter 21. The quiescent levelcalculator 22 compares the luminance information IR, IG, and IBregarding one frame image which has been supplied from the noise filter21 and the luminance information IR, IG, and IB regarding one framewhich is stored in the memory 23. The quiescent level calculator 22thereby determines a moving amount of the image and calculates thequiescent level LS on the basis of the determined moving amount. Thequiescent level LS may be expressed on a small scale (e.g., in 256stages) or on a large scale (e.g., in four stages). Further, thequiescent level calculator 22 supplies the generated quiescent level LSto the controller 11.

It is to be noted that, when noise is not severely significant, thenoise filter 21 may not be provided. Moreover, when an influence ofnoise still remains despite the provision of the noise filter 21 and themoving amount of a still image does not sufficiently decrease, forexample, a threshold may be provided for the moving amount. When themoving amount is equal to or less than this threshold, the quiescentlevel calculator 22 may determine that the image is a still image.Moreover, although the memory 23 is provided in the quiescent levelcalculator 22 in this example, the memory 23 may not necessarily beprovided and the quiescent level LS may be obtained by a simpler method.More specifically, for example, it is possible to divide a displayregion of the display section 40 into a plurality of sub-displayregions, to determine average levels of the luminance information IR,IG, and IB within each of the sub-display regions, and to obtain thequiescent level LS on the basis of variation in the average levels withtime. This method makes it possible to reduce power consumption andcost.

The controller 11 controls the signal processor 12 and the drivingsection 30 on the basis of the image signal Spic, the quiescent levelLS, and mode information Smode. More specifically, the controller 11controls whether to perform write driving on each of the sub-pixels 9 inthe display section 40, on the basis of the quiescent level LS.

FIG. 4 schematically illustrates operation of the sub-pixel 9. Part (A)thereof illustrates a case where the quiescent level LS is moderate, andPart (B) thereof illustrates a case where the quiescent level LS ishigh. In this example, the quiescent level LS is sufficiently low beforea timing t90 and at and after a timing t91, the quiescent level LS ismoderate in a period between the timings t90 and t91 (FIG. 4(A)) or thequiescent level LS is high in this period (FIG. 4(B)).

When the quiescent level LS is sufficiently low, the sub-pixel 9performs normal operation A within each frame period (1F). In the normaloperation A, the sub-pixel 9 performs write operation and performsthereafter light emitting operation. In other words, when the quiescentlevel LS is sufficiently low, a great movement appears in the image.Therefore, the sub-pixel 9 performs the write operation within eachframe period.

Moreover, when the quiescent level LS is moderate (FIG. 4(A)), thesub-pixel 9 performs intermittent write operation B. In thisintermittent write operation B, the sub-pixel 9 performs pre-suspensionoperation B1 in the first frame period and performs thereafter refreshoperation B3 in an intermittent manner. In each of the pre-suspensionoperation B1 and the refresh operation B3, the write operation isperformed using the pixel voltage Vsig higher than that in the normaloperation A, and light emitting operation is performed thereafter at alight emitting duty ratio DUTY lower than that in the normal operationA, as will be described later. Moreover, in write-suspended operationB2, the light emitting operation is performed at the light emitting dutyratio DUTY equivalent to those in both the pre-suspension operation B1and the refresh operation B3 without performing the write operation, aswill be described later. In this example, the sub-pixel 9 alternatelyrepeats the pre-suspension operation B1 or the refresh operation B3 andthe write-suspended operation B2 corresponding to one frame period. Inother words, in this example, the number of write-suspended frames NF isset to “1”. In other words, when the quiescent level LS is moderate, anintermediate movement appears in the image. Therefore, the sub-pixel 9performs the write operation in an intermittent manner.

Further, when the quiescent level LS is high (FIG. 4(B)), the sub-pixel9 performs the intermittent write operation B. In this intermittentwrite operation B, the sub-pixel 9 alternately repeats thepre-suspension operation B1 or the refresh operation B3 and thewrite-suspended operation B2 corresponding to four frame periods. Inother words, in this example, the number of write-suspended frames NF isset to “4”. In other words, when the quiescent level LS is high, a smallmovement appears in the image. Therefore, the sub-pixel 9 furtherincreases the number of write-suspended frames NF and performs the writeoperation in an intermittent manner.

In this way, the controller 11 dynamically sets the number ofwrite-suspended frames NF on the basis of the quiescent level LS.Further, the controller 11 supplies the control signal CTL to thedriving section 30, controlling the driving section 30 to perform theintermittent write operation B in accordance with the number ofwrite-suspended frames NF.

FIG. 5 illustrates operation of setting the number of write-suspendedframes NF on the basis of the quiescent level LS. In this example, thecontroller 11 sets the number of write-suspended frames NF to a largervalue as the quiescent level LS increases. In other words, as thequiescent level LS increases, a movement in the image decreases.Therefore, an image quality is less likely to be lowered even when thewrite operation is performed at lower frequency. Moreover, in thisexample, the controller 11 sets the number of write-suspended frames NFto a larger value as a frame rate FR increases. In other words, when theframe rate FR is high, a movement becomes smoother, in which case therisk of causing jerkiness is reduced. Therefore, image quality is lesslikely to be lowered even when the write operation is performed at lowerfrequency. In this way, the controller 11 sets the number ofwrite-suspended frames NF in accordance with the quiescent level LS andthe frame rate FR. Consequently, the display device 1 makes it possibleto reduce power consumption with a lower possibility of image qualitybeing lowered.

As described above, the controller 11 sets the number of write-suspendedframes NF on the basis of the quiescent level LS. Consequently, thedisplay device 1 makes it possible to reduce power consumption with alower possibility of image quality being lowered.

Moreover, the controller 11 also has a function of setting operation ofthe display device 1 on the basis of the operation mode informationSmode. The operation mode information Smode indicates an operation modeof the display device 1. The operation mode information Smode may besupplied from a system of an electronic apparatus employing this displaydevice 1. For example, the operation mode information Smode may be setin accordance with a power consumption setting of the electronicapparatus, an application, etc. Examples of the operation mode mayinclude a normal mode and a plurality of low power consumption modes(minimum, small, medium, etc.). The controller 11 sets the number ofwrite-suspended frames NF on the basis of this operation modeinformation Smode. More specifically, for example, the controller 11 mayset the number of write-suspended frames NF such that the number ofwrite-suspended frames NF becomes larger in the following order: thenormal mode, the low power consumption mode (medium), the low powerconsumption mode (small), and the low power consumption mode (minimum).Further, the controller 11 sets the light emitting duty ratio DUTY inthe normal operation A, the light emitting duty ratio DUTY in theintermittent write operation B, etc. on the basis of the operation modeinformation Smode. This makes it possible to set, for the display device1, power consumption and set image quality more flexibly in accordancewith the power consumption setting of the electronic apparatus, theapplication, etc.

Moreover, the controller 11 also has a function of directing the signalprocessor 12 and the driving section 30 to increase the pixel voltageVsig and directing the driving section 30 to shorten a light-emittingperiod of the sub-pixel 9, when the intermittent write operation B isperformed.

FIG. 6 illustrates the light emitting operation of the sub-pixel 9. InFIG. 6, the vertical axis represents luminance L of the sub-pixel 9, andthe horizontal axis represents time t. In this example, when performingthe intermittent write operation B, the sub-pixel 9 alternately repeatsthe pre-suspension operation B1 or the refresh operation B3 and thewrite-suspended operation B2 (B2(1) to B2(4)) corresponding to fourframe periods. The display device 1 sets the luminance L to be higherand the light emitting duty ratio DUTY to be lower when performing theintermittent write operation B than when performing the normal operationA. In this case, the light emitting duty ratio DUTY refers to the timeratio of the light-emitting period to one frame period. In this case,the display device 1 sets the luminance L and the light emitting dutyratio DUTY such that an average value of the luminance L over a frameperiod in the normal operation A is equal to an average value of theluminance L over a frame period in the write-suspended operation B2 andthe like.

More specifically, the controller 11 directs the signal processor 12 toincrease values of the luminance information IR, IG, and IB and directsthe driving section 30 to shorten the light-emitting period of thesub-pixel 9 via the control signal CTL. In this case, when determiningthat the values of the luminance information IR, IG, and IB are alreadysufficiently great and thus it is not possible to further increase thesevalues, the controller 11 directs the driving section 30 to change areference voltage for the DAC 34 via the control signal CTL, instead ofchanging the values of the luminance information IR, IG, and IB.

Moreover, the controller 11 also has a function of adjusting the lightemitting duty ratio DUTY in accordance with variation in the pixelvoltage Vsig of the sub-pixel 9 during the write-suspended operation B2,as will be described later. More specifically, for example, a leakagecurrent of the capacitor Cs or an off-leakage current of the writetransistor WSTr in the sub-pixel 9 may cause the pixel voltage Vsig tobe gradually lowered with time. In this case, the luminance L of thesub-pixel 9 may be gradually lowered with time. The display device 1adjusts the light emitting duty ratio DUTY so as to compensate for thislowering of the luminance L. This makes it possible to suppressdegradation of image quality in the display device 1.

The signal processor 12 subjects the image signal Spic to predeterminedimage processing on the basis of an instruction from the controller 11and outputs a result of this processing as the image signal Spic2. Morespecifically, when the intermittent write operation B is performed, thesignal processor 12 increases the values of the luminance informationIR, IG, and IB included in the image signal Spic, as described above.

In the foregoing example, the intermittent write operation B maycorrespond to one specific example of a “first drive mode” in thedisclosure. The normal operation A may correspond to one specificexample of a “second drive mode” in the disclosure. The controller 11,the signal processor 12, and the driving section 30 may correspond toone specific example of a “driving section” in the disclosure.

[Operation and Workings]

Next, a description will be given of operation and workings of thedisplay device 1 according to this embodiment.

(Outline of Overall Operation)

First, a description will be given of an outline of an overall operationof the display device 1, with reference to FIG. 1 and other drawings.The quiescent level detector 20 generates the quiescent level LS on thebasis of the image signal Spic. The controller 11 controls the signalprocessor 12 and the driving section 30 on the basis of the image signalSpic, the quiescent level LS, and the operation mode information Smode.More specifically, the controller 11 sets the number of write-suspendedframes NF on the basis of the quiescent level LS and the operation modeinformation Smode. Further, when the intermittent write operation B isperformed, the controller 11 directs the signal processor 12 and thedriving section 30 to increase the pixel voltage Vsig and directs thedriving section 30 to shorten the light-emitting period of the sub-pixel9. Furthermore, during the write-suspended operation B2, the controller11 adjusts the light emitting duty ratio DUTY in accordance withvariation in the pixel voltage Vsig for the sub-pixel 9. The signalprocessor 12 subjects the image signal Spic to predetermined imageprocessing on the basis of an instruction from the controller 11 andoutputs the result of this processing as the image signal Spic2. Thedriving section 30 drives the display section 40 on the basis of theimage signal Spic2 supplied from the signal processor 12 and the controlsignal CTL supplied from the controller 11. The display section 40displays an image on the basis of the driving operation performed by thedriving section 30.

(Detailed Operation)

Next, details of the operation of the sub-pixel 9 will be described. Thedescription will be given first regarding the normal operation A andthen regarding the write-suspended operation B2. It is to be noted thatdescriptions regarding the sub-pixel 9 in the normal operation A2, thepre-suspension operation B1, and the refresh operation B3 will beomitted, as these operations are similar to the normal operation A.

FIG. 7 illustrates a timing chart of the normal operation A of thesub-pixel 9. This drawing illustrates exemplary operation of a singlesub-pixel 9 of interest during display driving. In FIG. 7, Part (A)illustrates a waveform of a scanning signal WS, Part (B) illustrates awaveform of the power signal DS, Part (C) illustrates a waveform of thesignal Sig, Part (D) illustrates a waveform of a gate voltage Vg of thedrive transistor DRTr, and Part (E) illustrates a waveform of a sourcevoltage Vs of the drive transistor DRTr. In Parts (B) to (E) of FIG. 7,the respective waveforms are expressed using the same voltage axis.

Within one horizontal period (1H), the driving section 30 initializesthe sub-pixel 9 (an initialization period P1), makes a Vth correction tosuppress influence that element variations between the drive transistorsDRTr exert over image quality (a Vth correction period P2), and writesthe pixel voltage Vsig to the sub-pixel 9 while making a μ (mobility)correction, which is different from the Vth correction (writing·μcorrection period P3). Further, the light emitting element 49 in thesub-pixel 9 emits thereafter light at the luminance L according to thewritten pixel voltage Vsig (a light-emitting period P4). Details ofthese will be described below.

First, the power line driving section 32 sets the power signal DS to thevoltage Vini before the initialization period P1 (Part (B) of FIG. 7).In response thereto, the drive transistor DRTr is turned on, and thesource voltage Vs of the drive transistor DRTr is set to the voltageVini (Part (E) of FIG. 7).

Thereafter, the driving section 30 initializes the sub-pixel 9 duringthe period from the timing t2 to the timing t3 (the initializationperiod P1). More specifically, at the timing t2, the data line drivingsection 33 sets the signal Sig to the voltage Vofs (Part (C) of FIG. 7),and scan line driving sections 31A and 31B vary the voltage of thescanning signal WS from a low level to a high level (Part (A) of FIG.7). In response thereto, the write transistor WSTr is turned on, and thegate voltage Vg of the drive transistor DRTr is set to the voltage Vofs(Part (D) of FIG. 7). As a result, the gate-source voltage Vgs(=Vofs−Vini) of the drive transistor DRTr is set to a voltage higherthan a threshold voltage Vth of the drive transistor DRTr. In this way,the sub-pixel 9 is initialized.

Thereafter, the driving section 30 makes the Vth correction during theperiod from the timing t3 to timing t4 (the Vth correction period P2).More specifically, at the timing t3, the power line driving section 32varies the power signal DS from the voltage Vini to the voltage Vccp(Part (B) of FIG. 7). In response thereto, the drive transistor DRTroperates within its saturation region. A current Ids flows from thedrain to the source of the drive transistor DRTr, increasing the sourcevoltage Vs (Part (E) of FIG. 7). In this case, the source voltage Vs islower than the voltage Vcath at the cathode of the light emittingelement 49 in this example. Therefore, the light emitting element 49maintains its reversely-biased state. As a result, no current flowsthrough the light emitting element 49. By increasing the source voltageVs in this manner, the gate-source voltage Vgs is decreased, and thusthe current Ids is decreased. This negative feedback operation makes thecurrent Ids converge into “0” (zero). In other words, the current Idsconverges so that the gate-source voltage Vgs of the drive transistorDRTr becomes equal to the threshold voltage Vth of the drive transistorDRTr (Vgs=Vth).

Thereafter, at the timing t4, the scan line driving sections 31A and 31Bvary the voltage of the scanning signal WS from the high level to a lowlevel (Part (A) of FIG. 7). In response thereto, the write transistorWSTr is turned off. Further, the data line driving section 33 sets thesignal Sig to the pixel voltage Vsig at the timing t5 (FIG. 7(C)).

Thereafter, over the period from a timing t6 to timing t7 (the writing·μcorrection period P3), the driving section 30 writes the pixel voltageVsig to the sub-pixel 9 while making the μ correction. Morespecifically, the scan line driving sections 31A and 31B vary thevoltage of the scanning signal WS from a low level to a high level atthe timing t6 (Part (A) of FIG. 7). In response thereto, the writetransistor WSTr is turned on, and the gate voltage Vg of the drivetransistor DRTr increases from the voltage Vofs to the pixel voltageVsig (Part (D) of FIG. 7). In this case, the gate-source voltage Vgs ofthe drive transistor DRTr is higher than the threshold voltage Vth(Vgs>Vth). Since the current Ids flows from the drain to the source, thesource voltage Vs of the drive transistor DRTr increases (Part (E) ofFIG. 7). This negative feedback operation reduces influence of elementvariations between the drive transistors DRTr (the μ correction), andthe gate-source voltage Vgs of the drive transistor DRTr is set to avoltage Vemi according to the pixel voltage Vsig. It is to be noted thatan exemplary method of making the above μ correction is described inJapanese Unexamined Patent Application Publication No. 2006-215213.

Thereafter, the driving section 30 causes the sub-pixel 9 to emit lightover the period following the timing t7 (the light-emitting period P4).More specifically, at the timing t7, the scan line driving sections 31Aand 31B vary the voltage of the scanning signal WS from the high levelto a low level (Part (A) of FIG. 7). In response thereto, the writetransistor WSTr is turned off, and the gate of the drive transistor DRTris brought into a floating state. After that, the voltage between thetwo ends of the capacitor Cs, namely, the gate-source voltage Vgs of thedrive transistor DRTr is maintained. Further, with the current Idsflowing through the drive transistor DRTr, the source voltage Vs of thedrive transistor DRTr increases (Part (E) of FIG. 7). In accordancetherewith, the gate voltage Vg of the drive transistor DRTr alsoincreases (Part (D) of FIG. 7). Further, when the source voltage Vs ofthe drive transistor DRTr becomes larger than the sum of the thresholdvoltage Vel of the light emitting element 49 and the voltage Vcath(Vel+Vcath), a current flows between the anode and cathode of the lightemitting element 49. As a result, the light emitting element 49 emitslight. In other words, the source voltage Vs increases by an amountcorresponding to the element variations between the light emittingelements 49, and consequently the light emitting element 49 emits light.

Thereafter, after a period corresponding to the light emitting dutyratio DUTY has passed, the driving section 30 varies the power signal DSfrom the voltage Vccp to the voltage Vini. The light-emitting period P4is thus ended. It is to be noted that, in the normal operation A, thelight-emitting period P4 is ended in response to the variation of thepower signal DS from the voltage Vccp to the voltage Vini as describedabove. In each of the pre-suspension operation B1 and the refreshoperation B3, the light-emitting period P4 is ended in response to thevariation of the power signal DS from the voltage Vccp to the voltageVext.

FIG. 8 illustrates a timing chart of the write-suspended operation B2 ofthe sub-pixel 9. Part (A) thereof illustrates a waveform of the scanningsignal WS, Part (B) thereof illustrates a waveform of the power signalDS, Part (C) thereof illustrates a waveform of the signal Sig, Part (D)thereof illustrates a waveform of the gate voltage Vg of the drivetransistor DRTr, and Part (E) thereof illustrates a waveform of thesource voltage Vs of the drive transistor DRTr.

In the write-suspended operation B2, the voltage of the scanning signalWS is always kept at a low level. Therefore, to maintain the writetransistor WSTr in an off state, the gate-source voltage Vgs of thedrive transistor DRTr is maintained at the voltage Vemi that has beenset during the writing·μ correction period P3. It is to be noted thatthis description is given without taking into consideration a leakagecurrent of the capacitor Cs and the like, for the sake of convenience.

First, the power line driving section 32 sets the power signal DS to thevoltage ext (Part (B) of FIG. 8). In response thereto, the drivetransistor DRTr is turned on, and the source voltage Vs of the drivetransistor DRTr is set to the voltage Vext (Part (E) of FIG. 8).

Further, the driving section 30 causes the sub-pixel 9 to emit lightover the period at and after timing t13 (the light-emitting period P4).More specifically, at the timing t13, the power line driving section 32varies the power signal DS from the voltage Vext to the voltage Vccp(Part (B) of FIG. 8). As a result, the drive transistor DRTr operateswithin its saturation region. Further, the current Ids flows from thedrain to the source, and the source voltage Vs of the drive transistorDRTr increases (Part (E) of FIG. 8). In accordance therewith, the gatevoltage Vg of the drive transistor DRTr also increases (Part (D) of FIG.8). Further, when the source voltage Vs of the drive transistor DRTrbecomes larger than the sum (Vel+Vcath) of the threshold voltage Vel ofthe light emitting element 49 and the voltage Vcath, a current flowsbetween the anode and the cathode of the light emitting element 49. As aresult, the light emitting element 49 emits light. In other words, thesource voltage Vs increases by an amount corresponding to the elementvariations in the light emitting elements 49, and consequently, thelight emitting element 49 emits light.

Thereafter, after a period corresponding to the light emitting dutyratio DUTY has passed, the driving section 30 varies the power signal DSfrom the voltage Vccp to the voltage Vext. The light-emitting period P4is thus ended.

In the intermittent write operation B, the sub-pixel 9 alternatelyrepeats the pre-suspension operation B1 or the refresh operation B3 andthe write-suspended operation B2 corresponding to the predeterminednumber of frame periods. In this write-suspended operation B2, thesub-pixel 9 performs the light emitting operation without performing thewrite operation. Therefore, when a leakage current of the capacitor Cs,an off-leakage current of the write transistor WSTr, etc. are present,the pixel voltage Vsig may be gradually lowered with time, so that theluminance L of the sub-pixel 9 may be gradually lowered. The displaydevice 1 adjusts the light emitting duty ratio DUTY so as to compensatefor this lowering of the luminance L. Details of this operation will bedescribed below.

FIG. 9 illustrates exemplary operation of the sub-pixel 9 in theintermittent write operation B. Part (A) thereof illustrates theluminance L of the sub-pixel 9, Part (B) thereof illustrates an integralvalue (display luminance LD) of the luminance L over each light-emittingperiod P4, and Part (C) thereof illustrates time duration (lightemitting time duration W) of each light-emitting period P4. FIG. 9 isexaggerated for the sake of convenience in explanation. In this example,the sub-pixel 9 alternately repeats the pre-suspension operation B1 orthe refresh operation B3 and the write-suspended operation B2 (B2(1) toB2(4)) corresponding to four frame periods.

In the display device 1, as illustrated in Part (A) of FIG. 9, theluminance L is lowered with time during the write-suspended operationB2, due to a leakage current of the capacitor Cs, etc., for example. Thecontroller 11 adjusts the light emitting duty ratio DUTY so as tocompensate for the lowering of the luminance L. More specifically, whilekeeping a length of the frame period constant, the controller 11 narrowsthe light emitting time duration W when the luminance L is high orwidens the light emitting time duration W when the luminance L is low(Part (C) of FIG. 9), for example. This makes it possible to keep thedisplay luminance LD substantially constant in the display device 1, asillustrated in Part (B) of FIG. 9.

In this case, the controller 11 adjusts the light emitting duty ratioDUTY such that the light emitting time duration W does not vary rapidly.More specifically, in this example, the controller 11 sets the lightemitting duty ratios DUTY in the pre-suspension operation B1 and therefresh operation B3 to be higher, by a period Δ1, than the lightemitting duty ratio DUTY in write-suspended operation B2(1) to beperformed next. Likewise, the controller 11 sets the light emitting dutyratio DUTY in the third write-suspended operation B2(3) to be higherthan the light emitting duty ratio DUTY in the fourth write-suspendedoperation B2(4). In this way, the display device 1 makes it possible toreduce the possibility of a user perceiving blinks (so-called flickers)in comparison with a display device 1R according to Comparative Example(described later), thus enhancing image quality.

Comparative Example

Next, the display device 1R according to Comparative Example will bedescribed. Comparative Example uses a method of adjusting the lightemitting duty ratio DUTY which is different from that of the displaydevice 1 according to the present embodiment. More specifically, in thepresent embodiment (FIG. 1, FIG. 9, etc.), the display device 1R isconfigured using the controller 11 that adjusts the light emitting dutyratio DUTY such that the display luminance LD is kept substantiallyconstant and the light emitting time duration W does not vary rapidly.In contrast to this, in Comparative Example, the display device 1R isconfigured using a controller 11R that does not take into considerationthe light emitting time duration W and adjusts the light emitting dutyratio DUTY such that the display luminance LD is kept constant. Otherconfigurations are substantially the same as those in the presentembodiment (FIG. 1).

FIG. 10 illustrates exemplary operation of the sub-pixel 9 in thedisplay device 1R. Part (A) thereof illustrates the luminance L of thesub-pixel 9. Part (B) thereof illustrates the display luminance LD. Part(C) thereof illustrates the light emitting time duration W. Asillustrated in Part (A) of FIG. 10, the luminance L of the displaydevice 1R is lowered with time. A controller 11D adjusts the lightemitting duty ratio DUTY so as to compensate for this lowering of theluminance L. More specifically, the controller 11D gradually widens thelight emitting time duration W with time. In other words, the controller11D adjusts the light emitting duty ratio DUTY such that the displayluminance LD is kept constant, as illustrated in Part (B) of FIG. 10. Asa result, the light emitting time duration W is gradually widened withtime but rapidly narrowed in the refresh operation B3 (Part (C) of FIG.10).

In the display device 1R according to Comparative Example, as describedabove, the light emitting time duration W varies rapidly every time therefresh operation B3 is performed. As a result, the display device 1Rmay cause blinks (so-called flickers) in an image. This intermittentwrite operation B is performed especially when the quiescent level LS ishigh (only a small movement appears in a display image). Therefore,flickers tend to appear more prominently than when an image with a greatmovement is displayed. Furthermore, a user tends to clearly perceivesuch low-frequency flickers. More specifically, humans tend to clearlyperceive a flicker having a frequency of about 70 Hz or lower. Therefresh operation B3 is performed less frequently as the quiescent levelLS increases. Consequently, the user tends to perceive flickers moreclearly as the quiescent level LS increases. An occurrence of suchflickers may cause the user to feel that image quality is lowered.

In contrast, in the display device 1 according to the presentembodiment, the controller 11 adjusts the light emitting duty ratio DUTYsuch that the light emitting time duration W does not vary rapidly, asdescribed in FIG. 9. In this way, the display device 1 gradually variesthe light emitting time duration W, thereby making it possible to reducethe possibility of causing a user to perceive flickers. This makes itpossible to enhance image quality.

Moreover, the display device 1 sets the light emitting duty ratio DUTYto a smaller value when the intermittent write operation B is performedthan when the normal operation A is performed, as illustrated in FIG. 6.This makes it possible to reserve a margin used to vary the lightemitting duty ratio DUTY to a large value during the intermittent writeoperation B. As a result, it is possible to compensate for lowering ofthe luminance L appropriately even when the number of write-suspendedframes NF is set to a large value, for example.

Effects

In the embodiment described above, when the intermittent write operationis performed, the light emitting duty ratio is adjusted taking intoconsideration lowering of the pixel voltage. Therefore, it is possibleto enhance image quality.

In the present embodiment, the light emitting duty ratio is adjustedsuch that the light emitting time duration does not vary rapidly.Therefore, it is possible to enhance image quality.

In the present embodiment, when the light emitting duty ratio is set toa smaller value when the intermittent write operation is performed thanwhen the normal operation is performed. Therefore, it is possible toreserve a margin for the light emitting duty ratio, thereby compensatingfor lowering of luminance appropriately.

[Modification 1-1]

In the embodiment described above, the sub-pixel 9 emits light onceevery time each of the pre-suspension operation B1, the write-suspendedoperation B2, and the refresh operation B3 is performed, as illustratedin FIG. 6 and other drawings. However, this scheme is not limiting.Alternatively, the sub-pixel 9 may emit light multiple times, forexample, as in a display device 1A illustrated in FIG. 11 and FIG. 12.In this example, the sub-pixel 9 emits light twice every time each ofthe pre-suspension operation B1, the write-suspended operation B2, andthe refresh operation B3 is performed. In this case, the luminance L andthe light emitting duty ratio DUTY are also adjusted such that theaverage value of the luminance L over one frame period upon the normaloperation A becomes equal to the average value of the luminance L overone frame period upon the write-suspended operation B2 or the like. Timelengths of the two light-emitting periods may be set to either the samevalue or different values. In this example, the light emitting timeduration W of each light-emitting period P4 in the pre-suspensionoperation B1 and the refresh operation B3 is set to be longer than thelight emitting time duration W of each light-emitting period P4 in thewrite-suspended operation B2(1) to be performed next. Furthermore, thelight emitting time duration W of each light-emitting period P4 in thethird write-suspended operation B2(3) is set to be longer than the lightemitting time duration W of each light-emitting period P4 in the fourthwrite-suspended operation B2(4).

It is to be noted that, in this example, the sub-pixel 9 emits lighttwice every time each of the pre-suspension operation B1, thewrite-suspended operation B2, and the refresh operation B3 is performed;however, this scheme is not limiting. Alternatively, the sub-pixel 9 mayemit light three times or more, for example. More specifically, thesub-pixel 9 may preferably emit light at frequency at which a user doesnot perceive blinks (e.g., 70 times or more per second).

[Modification 1-2]

In the embodiment described above, the number of write-suspended framesNF are dynamically set to all the display regions of the display section40; however, this scheme is not limiting. Alternatively, the number ofwrite-suspended frames NF may be dynamically set to only portions of thedisplay regions of the display section 40. A display device 1B accordingto the present modification will be described below in detail.

FIG. 13 illustrates an exemplary configuration of the display device 1B.The display device 1B is provided with a controller 11B. The controller11B controls the signal processor 12 and the driving section 30, in amanner similar to that of the controller 11 according to the embodimentdescribed above. In this case, the controller 11B controls the signalprocessor 12 and the driving section 30 on the basis of contentinformation Sc. Herein, the content information Sc may be supplied fromanother circuit, for example, and may represent a type (e.g., movie,data broadcast, etc.) of a content indicated by the image signal Spic.

FIG. 14A and FIG. 14B each illustrate operation of the controller 11Bwhich is based on the content information Sc. As one example, when thecontent is a movie film, on the basis of the content information Sc, thecontroller 11B dynamically sets the number of write-suspended frames NFfor a middle region R22 on the basis of the quiescent level LS and stopswrite driving within an upper region R21 and a lower region R23. Theregion R22 is a portion of a display region S in the display section 40on which a movie image is to be displayed. Each of the upper region R21and the lower region R23 is a portion of the display region S on which aso-called black zone is to be displayed. This operation makes itpossible to reduce power consumption within the region R22 with reducedpossibility of image quality being lowered. This allows for reduction inpower consumption within the regions R21 and R23. Moreover, as anotherexample, when the content is a data broadcast, on the basis of thecontent information Sc, the controller 11B dynamically sets the numberof write-suspended frames NF for a middle region R31 on the basis of thequiescent level LS and sets predetermined relatively-large number for aperipheral region R32 as the number of write-suspended frames NF. Themiddle region R31 has a great movement in an image. The peripheralregion R32 has a small movement in an image. This operation makes itpossible to reduce power consumption within the region R31 with reducedpossibility of image quality being lowered. This allows for reduction inpower consumption within the region R32.

[Modification 1-3]

In the embodiment described above, the quiescent level LS is determinedon the basis of the image signal Spic; however, this scheme is notlimiting. Alternatively, for example, the quiescent level LS may besupplied from the outside, as in a display device 1C illustrated in FIG.15. The display device 1C includes the controller 11, the signalprocessor 12, the driving section 30, and the display section 40. Inother words, the display device 1C is equivalent to the display device 1according to the embodiment described above from which the quiescentlevel detector 20 is removed. This controller 11 is supplied with thequiescent level LS from the outside. The quiescent level LS may begenerated by an upstream circuit, for example. Examples of the upstreamcircuit may include an MPEG (moving picture experts group) decoder and aframe rate conversion circuit.

[Other Modifications]

Moreover, two or more of these modifications may be combined together.

2. Second Embodiment

Next, a display device 2 according to a second embodiment will bedescribed. In this embodiment, the frame period is configured to have avariable length when the intermittent write operation B is performed. Itis to be noted that, herein, constituent elements substantially the sameas those in the display device 1 according to the first embodimentdescribed above are denoted with the same reference codes and will notbe further described where appropriate.

As illustrated in FIG. 1, the display device 2 is provided with acontroller 51. The controller 51 adjusts the light emitting timeduration W in accordance with variation in the pixel voltage Vsig forthe sub-pixel 9 during the write-suspended operation B2, as with thecontroller 11 according to the first embodiment described above. In thiscase, the controller 51 changes the length of the frame period whileadjusting the light emitting time duration W such that display luminanceLD is kept substantially constant.

FIG. 16 illustrates exemplary operation of the sub-pixel 9 in theintermittent write operation B. Part (A) thereof illustrates theluminance L of the sub-pixel 9, Part (B) thereof illustrates an integralvalue (display luminance LD) of the luminance L over each light-emittingperiod P4, and Part (C) thereof illustrates time duration (the lightemitting time duration W) of each light-emitting period P4. FIG. 16 isexaggerated for the sake of convenience in explanation. In this example,the sub-pixel 9 alternately repeats the pre-suspension operation B1 orthe refresh operation B3 and the write-suspended operation B2 (B2(1) toB2(4)) corresponding to four frame periods. It is to be noted that thesub-pixel 9 emits light twice during each of the pre-suspensionoperation B1, the write-suspended operation B2, and the refreshoperation B3; however, this scheme is not limiting. The sub-pixel 9 mayemit light once or may emit light three or more times.

The controller 51 adjusts the light emitting time duration W so as tocompensate for lowering of the luminance L (Part (A) of FIG. 16). Inthis case, the controller 51 controls the operation such that aninterval between adjacent light-emitting periods P4 is kept constant.Under this control, in the display device 2, an operational period ofeach of the pre-suspension operation B1, the write-suspended operationsB2(1) to B2(4), and the refresh operation B3 varies depending on thelight emitting time duration W. In other words, in the display device 2,the length of the frame period varies during the intermittent writeoperation B. This makes it possible to increase flexibility of operationin the display device 2, enhancing image quality.

Moreover, the controller 51 sets the light emitting time duration W ofeach light-emitting period P4 in the pre-suspension operation B1 and therefresh operation B3 to be nearly equal to the light emitting timeduration W of each light-emitting period P4 in the write-suspendedoperation B2(1). In addition, the controller 51 sets the light emittingtime duration W of each light-emitting period P4 in the write-suspendedoperation B2(3) to be nearly equal to the light emitting time duration Wof each light-emitting period P4 in the write-suspended operation B2(4).In this way, the display device 2 suppresses rapid variation in thelight emitting time duration W, making it possible to reduce thepossibility of a user perceiving blinks in the image. This makes itpossible to enhance image quality.

In this embodiment, as described above, the length of the frame periodvaries in the intermittent write operation. This makes it possible toincrease flexibility of operation, enhancing image quality. Othereffects are substantially the same as those in the first embodimentdescribed above.

[Modification 2-1]

In the embodiment described above, the light emitting time duration W inthe pre-suspension operation B1 and the refresh operation B3 is set tobe nearly equal to the light emitting time duration W in thewrite-suspended operation B2(1). In addition, the light emitting timeduration W in the write-suspended operation B2(3) is set to be nearlyequal to the light emitting time duration W in the write-suspendedoperation B2(4). However, this scheme is not limiting. Alternatively,for example, as illustrated in FIG. 17, the light emitting time durationW in the pre-suspension operation B1 and the refresh operation B3 may beset to be longer than the light emitting time duration W in thewrite-suspended operation B2(1). In addition, the light emitting timeduration W in the write-suspended operation B2(3) may be set to belonger than the light emitting time duration W in the write-suspendedoperation B2(4).

[Modification 2-2]

Moreover, as illustrated in FIG. 18, for example, the light emittingtime duration W may be gradually widened so as to compensate forlowering of the luminance L, and the light emitting time duration W maybe adjusted such that the display luminance LD is kept constant. Also inthis case, it is possible to increase flexibility of operation, thusenhancing image quality.

[Modification 2-3]

In the embodiment described above, as illustrated in FIG. 16 and otherdrawings, the sub-pixel 9 emits light twice during each of thepre-suspension operation B1, the write-suspended operation B2, and therefresh operation B3; however, this scheme is not limiting.Alternatively, the sub-pixel 9 may emit light once, for example, asillustrated in FIG. 19 and FIG. 20. FIG. 19 corresponds to the exampleof the second embodiment described above (FIG. 16). FIG. 20 correspondsto the example of the modification 2-1 described above (FIG. 17).

[Other Modifications]

The modifications of the first embodiment described above may be appliedto the display device 2 according to the embodiment described above.

3. Exemplary Applications

Next, a description will be given of exemplary applications of thedisplay device described in any of the foregoing embodiments. Thedisplay device in any of the foregoing embodiments is applicable todisplay devices in electronic apparatuses in various fields whichperform display on the basis of an image signal received from theoutside or an image signal generated therein. Examples of suchelectronic apparatuses may include a television apparatus, an electronicbook, a smartphone (multifunction portable phone), a digital camera, alaptop personal computer, a video camera, and a head mount display.

FIG. 21 is an appearance of outside of a smartphone 300. This smartphone300 may include an operation section 310 and a display section 320. Thedisplay section 320 may be configured of the foregoing display device.

A display device described in any of the foregoing embodiments isapplicable to various electronic apparatuses. The present technologyreduces power consumption and enhances image quality. The presenttechnology contributes greatly to prolonged driven time of a battery ina portable electronic apparatus and improved image quality of theportable electronic apparatus.

The present technology has been described referring to some embodiments,modifications, and exemplary applications to electronic apparatuses.However, the present technology is not limited to such embodiments andthe like and may be variously modifiable.

As one example, although a single capacitor Cs is disposed in each ofthe sub-pixels 9 in the foregoing embodiments, a configuration of eachof the sub-pixels 9 is not limiting. Alternatively, a capacitor Csub maybe disposed, for example, as in a sub-pixel 7 illustrated in FIG. 22.The capacitor Csub may have one end coupled to the anode of the lightemitting element 49 and the other end coupled to the cathode of thelight emitting element 49. In short, the sub-pixel 7 may be configuredusing two transistors (the write transistor WSTr and the drivetransistor DRTr) and two capacitors Cs and Csub, namely, may have aso-called “2Tr2C” configuration.

As another example, the present technology is applicable to various usesin which an interval between one write operation and the subsequentwrite operation is set to 30 [msec] or longer.

It is to be noted that the effects described herein are mere exemplaryand thus not limiting. Further, any other effect may be provided.

It is to be noted that the present technology may be configured asfollows.

(1) A display device including:

a display section having a plurality of unit pixels; and

a driving section that, in a first drive mode, performs write drivingand thereafter performs light emission driving in a plurality oflight-emitting periods on each of the unit pixels, wherein

one of predetermined number of light-emitting periods out of theplurality of light-emitting periods other than a first light-emittingperiod is longer than the first light-emitting period, and

another one of the predetermined number of light-emitting periods isshorter than the first light-emitting period.

(2) The display device according to (1), wherein time intervals betweenstart timings of adjacent ones of the light-emitting periods are equalto each other.

(3) The display device according to (1), wherein, of time intervalsbetween start timings of adjacent ones of the light-emitting periods,one time interval is different from another time interval.

(4) The display device according to (3), wherein two non-light-emittingperiods sandwiching each of the light-emitting periods have same length.

(5) The display device according to any one of (1) to (4), wherein thedriving section sets, on a basis of an image signal, a singlelight-emitting period in a period corresponding to a frame periodindicated by the image signal, and drives each of the unit pixels.

(6) The display device according to any one of (1) to (4), wherein thedriving section sets, on a basis of an image signal, two or morelight-emitting periods in a period corresponding to a frame periodindicated by the image signal, and drives each of the unit pixels.

(7) The display device according to any one of (1) to (6), wherein thedriving section selects one from among a plurality of drive modesincluding the first drive mode and drives each of the unit pixels in theselected drive mode.

(8) The display device according to (7), wherein

the plurality of drives include a second drive mode, and

in the second drive mode, the driving section performs the write drivingand thereafter performs the light emission driving in a singlelight-emitting period on each of the unit pixels.

(9) The display device according to (8), wherein each of thelight-emitting periods in the first drive mode is shorter than each ofthe light-emitting periods in the second drive mode.

(10) The display device according to (8) or (9), wherein

the driving section writes a pixel voltage to each of the unit pixelsupon the write driving, and

a luminance level indicated by the pixel voltage in the first drive modeis higher than a luminance level indicated by the pixel voltage in thesecond drive mode.

(11) The display device according to any one of (7) to (10), wherein thedriving section selects one from among the plurality of drive modes on abasis of a moving amount in an image to be displayed in the displaysection.

(12) The display device according to any one of (7) to (11), wherein thedriving section selects one from among the plurality of drive modes on abasis of content of an image to be displayed in the display section.

(13) A display device including:

a display section having a plurality of unit pixels; and

a driving section that, in a first drive mode, performs write drivingand thereafter performs light emission driving in a plurality oflight-emitting periods on each of the unit pixels, wherein,

of time intervals between start timings of adjacent ones of thelight-emitting periods, one time interval is different from another timeinterval.

(14) The display device according to (13), wherein twonon-light-emitting periods sandwiching each of the light-emittingperiods have same length.

(15) The display device according to (13) or (14), wherein one ofpredetermined number of light-emitting periods out of the plurality oflight-emitting periods other than a first light-emitting period islonger than the first light-emitting period.

(16) The display device according to any one of (13) to (15), wherein,of two adjacent ones of the light-emitting periods, a length of a laterlight-emitting period is equal to or more than a length of an earlierlight-emitting period.

(17) The display device according to any one of (13) to (15), whereinthe first light-emitting period is longer than one of the predeterminednumber of light-emitting periods.

(18) A driving method including:

preparing an image signal;

in a first drive mode, performing write driving based on the imagesignal and thereafter performing light emission driving in a pluralityof light-emitting periods on each of unit pixels; and,

upon the light emission driving, setting one of predetermined number oflight-emitting periods out of the plurality of light-emitting periodsother than a first light-emitting period to be longer than the firstlight-emitting period, and setting another one of the predeterminednumber of light-emitting periods to be shorter than the firstlight-emitting period.

(19) An electronic apparatus including:

a display device; and

a controller that controls operation of the display device, the displaydevice including

-   -   a display section having a plurality of unit pixels, and    -   a driving section that, in a first drive mode, performs write        driving and thereafter performs light emission driving in a        plurality of light-emitting periods on each of the unit pixels,        wherein

one of predetermined number of light-emitting periods out of theplurality of light-emitting periods other than a first light-emittingperiod is longer than the first light-emitting period, and

another one of the predetermined number of light-emitting periods isshorter than the first light-emitting period.

This application claims the benefit of priority from Japanese PriorityPatent Application JP 2014-092770 filed Apr. 28, 2014, the entirecontents of each which is incorporated herein by reference.

It should be understood by those skilled in the art that variousmodifications, combinations, sub-combinations, and alterations may occurdepending on design requirements and other factors insofar as they arewithin the scope of the appended claims or the equivalents thereof.

The invention claimed is:
 1. A display device comprising: a displaysection having a plurality of unit pixels; and a driving section that,in a first drive mode performed over a plurality of consecutive frameperiods indicated by an image signal, performs write driving operations,each of which is performed in one frame period and is followed by anlight emission driving operations, and thereafter performs lightemission driving operations, each of which is performed within one frameperiod with no write operation, in a plurality of light-emitting periodson each of the unit pixels, wherein: one of predetermined number oflight-emitting periods out of the plurality of light-emitting periodsother than a first light-emitting period is longer than the firstlight-emitting period, and another one of the predetermined number oflight-emitting periods is shorter than the first light-emitting period.2. The display device according to claim 1, wherein time intervalsbetween start timings of adjacent ones of the light-emitting periods areequal to each other.
 3. The display device according to claim 1,wherein, of time intervals between start timings of adjacent ones of thelight-emitting periods, one time interval is different from another timeinterval.
 4. The display device according to claim 3, wherein twonon-light-emitting periods sandwiching each of the light-emittingperiods have same length.
 5. The display device according to claim 1,wherein the driving section sets, on a basis of the image signal, a onelight-emitting period within one frame period indicated by the imagesignal, and drives each of the unit pixels.
 6. The display deviceaccording to claim 1, wherein the driving section sets, on a basis ofthe image signal, two or more light-emitting periods within one frameperiod indicated by the image signal, and drives each of the unitpixels.
 7. The display device according to claim 1, wherein the drivingsection selects one from among a plurality of drive modes including thefirst drive mode and drives each of the unit pixels in the selecteddrive mode.
 8. The display device according to claim 7, wherein: theplurality of drives include a second drive mode, and in the second drivemode, the driving section performs the write driving operation andthereafter performs the light emission driving operation within oneframe period on each of the unit pixels.
 9. The display device accordingto claim 8, wherein each of the light-emitting periods in the firstdrive mode is shorter than each of the light-emitting periods in thesecond drive mode.
 10. The display device according to claim 8, wherein:the driving section writes a pixel voltage to each of the unit pixelsupon the write driving operation, and a luminance level indicated by thepixel voltage in the first drive mode is higher than a luminance levelindicated by the pixel voltage in the second drive mode.
 11. The displaydevice according to claim 7, wherein the driving section selects onefrom among the plurality of drive modes on a basis of a moving amount inan image to be displayed in the display section.
 12. The display deviceaccording to claim 7, wherein the driving section selects one from amongthe plurality of drive modes on a basis of content of an image to bedisplayed in the display section.
 13. A display device comprising: adisplay section having a plurality of unit pixels; and a driving sectionthat, in a first drive mode performed over a plurality of consecutiveframe periods indicated by an image signal, performs write drivingoperations, each of which is performed in one frame period and isfollowed by an light emission driving operations, and thereafterperforms light emission driving operations, each of which is performedin one frame period with no write operation, in a plurality oflight-emitting periods on each of the unit pixels, wherein, of timeintervals between start timings of adjacent ones of the light-emittingperiods, one time interval is different from another time interval. 14.The display device according to claim 13, wherein two non-light-emittingperiods sandwiching each of the light-emitting periods have same length.15. The display device according to claim 13, wherein one ofpredetermined number of light-emitting periods out of the plurality oflight-emitting periods other than a first light-emitting period islonger than the first light-emitting period.
 16. The display deviceaccording to claim 13, wherein, of two adjacent ones of thelight-emitting periods, a length of a later light-emitting period isequal to or more than a length of an earlier light-emitting period. 17.The display device according to claim 13, wherein the firstlight-emitting period is longer than one of the predetermined number oflight-emitting periods.
 18. A driving method comprising: preparing animage signal; in a first drive mode performed over a plurality ofconsecutive frame periods indicated by the image signal, performing,based on the image signal, write driving operations, each of which isperformed in one frame period and is followed by an light emissiondriving operations, and thereafter performing light emission drivingoperations, each of which is performed in one frame period with no writeoperation, in a plurality of light-emitting periods on each of unitpixels; and, upon the light emission driving, setting one ofpredetermined number of light-emitting periods out of the plurality oflight-emitting periods other than a first light-emitting period to belonger than the first light-emitting period, and setting another one ofthe predetermined number of light-emitting periods to be shorter thanthe first light-emitting period.
 19. An electronic apparatus comprising:a display device; and a controller that controls operation of thedisplay device, the display device including a display section having aplurality of unit pixels, and a driving section that, in a first drivemode performed over a plurality of consecutive frame periods indicatedby the image signal, performs write driving operations, each of which isperformed in one frame period and is followed by an light emissiondriving operations, and thereafter performs light emission drivingoperations, each of which is performed in one frame period with no writeoperation, in a plurality of light-emitting periods on each of the unitpixels, wherein: one of predetermined number of light-emitting periodsout of the plurality of light-emitting periods other than a firstlight-emitting period is longer than the first light-emitting period,and another one of the predetermined number of light-emitting periods isshorter than the first light-emitting period.